Reinforced concrete is widely used in many structures. For various reasons, reinforced concrete may deteriorate over time. For example, in locations where the weather is often wet and cold, salt is used to de-ice roads and parking lots. The salt causes deterioration of the concrete and, ultimately, corrosion of rebar in the reinforced concrete, potentially affecting the load-bearing ability of the reinforced concrete. Corrosion of the rebar is the result of weathering. As is well known in the art, ambient temperature fluctuations and the presence of salt tend to increase the rate of corrosion.
A typical reinforced concrete beam 10 is illustrated in FIG. 1. The beam 10 includes a body 12 in which rebar 14 is positioned. As is well known in the art, the rebar 14 is made of steel, and the body 12 is made of concrete that generally or at least substantially encases the rebar 14. Although only one rebar element 14 is illustrated in FIG. 1, it will be understood that the reinforced concrete beam 10 may alternatively include a number of elongate rebar elements, positioned substantially parallel to each other. As can be seen in FIG. 1, the rebar 14 is generally not directly observable, because it is encased in the body 12. At its ends, the rebar 14 may be directly observable, depending on the position of the reinforced concrete beam 10 in the structure in which it is included. In FIG. 1, a corroded area 16 is indicated by dashed lines, for clarity of illustration. Corrosion of the rebar 14 may occur at any point or points along the length of the rebar, and therefore the rebar may have significant corrosion that is not directly observable, if the body is left intact. (As will be described, the balance of the drawings illustrate the present invention.)
Corrosion of the rebar undermines the load-bearing capacity of the reinforced concrete in which the rebar is located. Therefore, detection of such corrosion can be critical. As is well known in the art, detecting corrosion of the rebar in reinforced concrete in an existing structure in most cases would not be possible with visual methods, or without destruction of at least part of the reinforced concrete. However, visual detection or destructive testing of the reinforced concrete in an existing structure are also usually not feasible.
In the prior art, corrosion may be detected when the concrete at a readily accessible portion of the structure has deteriorated to the extent that the corroded rebar is exposed. However, at that point, the poor condition of the reinforced concrete may require emergency action to repair the structure. Also, repairs are of necessity limited to damaged areas that are exposed, and such repairs would not address other damage that may have occurred to the rebar elsewhere in the reinforced concrete.